3.1 Introduction

The previous two chapters introduced the general geomodeling workflow as well as geostatistics. This chapter and the next two review how geoscientists can contribute to a reservoir modeling project. We focus here on geologists, before looking at the collaboration with petrophysicists (chapter 4) and then with geophysicists (chapter 5). Seismic data is not available for all reservoirs or at least not in the initial stages of most projects. For this reason, this chapter and the next one on petrophysics present techniques based on wells only. These techniques will be reviewed in the chapter on geophysics, to take seismic into account.

The role of geologists is to interpret the available well (and seismic) data to characterize the reservoir. As far as reservoir modeling is concerned, this leads to two different types of collaboration (Figure 1). On one hand, the geologist does all the interpretation before the modeling is started. Once the interpretation is complete, it is fed into the geomodeling workflow. The other approach is one where the geologist still starts his/her interpretation before the modeling begins, but he/she also uses the reservoir model and the visualization and interpretation tools embedded in the reservoir modeling software to test, improve and finalize his/her interpretation while the modeling is in progress.

The first type of collaboration is still popular as it corresponds to the traditional separation of tasks in teams: one specialist accomplishes a task and the outcomes become the input to the next specialist’s work. Unfortunately, this approach leads to less integration between specialists and sometimes it can potentially lead to misinterpretation of the reservoir.

The second type of collaboration requires more project management, as tasks are partly done in parallel. This increases the likelihood of data, ideas and knowledge integration within the team. We favour the second approach in this paper and that we will support in the subsequent papers in this series (both for collaboration with geoscientists and with engineers in the second half of the year).

In the next two sections, we illustrate the benefit of linking geological interpretation and reservoir modeling. The fourth section explains how geologists can guide the geostatistical algorithms of facies modeling by defining vertical proportion curves (VPC) and facies proportion maps. It is also important that the geologist helps the modeler in capturing the ranges of uncertainties associated to these inputs. This will be the focus of the last section.

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